1. Field of the Invention
This invention relates to compositions useful for preparing polishes for floors, furniture, et al. having improved durability. Compositions of this invention are floor polish vehicle compositions comprising a water insoluble emulsion copolymer containing acid functional residues, a polyvalent metal ionic crosslinking agent, and a basic salt of an alkaline metal. The floor polish vehicle compositions of this invention are useful in preparing floor polish compositions which yield floor polishes and furniture polishes having improved durability.
2. Brief Description of the Prior Art
Ionically crosslinked floor polish vehicle compositions are well known in the prior art. A floor polish vehicle composition is defined to include an aqueous dispersion of a water insoluble synthetic resin film former and water soluble or dispersible metal salts and complexes. Floor polish compositions are defined to include floor polish vehicle compositions, alkali soluble resins, plasticizers, waxes, preservatives, dispersing agents, coalescing agents, leveling agents and the like.
Floor polish compositions based on aqueous dispersions of water insoluble emulsion copolymers containing acid functional residues and ionically crosslinked with polyvalent metal ions or complex crosslinking agents are well known in the art. Such coating compositions are disclosed in U.S. Pat. No. 3,328,325, granted June 27, 1967, to R. E. Zdanowski; U.S. Pat. No. 3,573,239, granted Mar. 30, 1971 to R. E. Zdanowski; U.S. Pat. No. 3,467,610, granted Sept. 16, 1969, to I. S. Fiarman et al.; U.S. Pat. No. 3,554,790, granted Jan. 12, 1971 to D. R. Gehman et al.; and U.S. Pat. No. 3,711,436, granted Jan. 16, 1973, to C. J. Oliver.
One important characteristic of the temporary protective film obtained from floor polish compositions is its resistance to deterioration resulting from pedestrian traffic. The greater its resistance, the more durable the floor polish is said to be. The general property of durability can be measured in a variety of ways. For example, scuff and scratch resistance, retention of film gloss, powder resistance, soil resistance, and black heel mark resistance are all well recognized in the floor polish art as indicia of durability. Acrylic polymers and copolymers are the most commonly used class of resins in floor finishes. It is well known, and practiced, that improved wear resistance in a formulated polish may be obtained by (a) increasing the polymer molecular weight, (b) increasing the copolymeric content of hard (that is, high glass transition temperature) monomers, (c) decreasing the copolymeric styrene content (if any), (d) increasing the polymeric acid functionality, and (e) increasing the level of polyvalent metal crosslinking agent. Each of these alternative routes toward improved wear resistance, when practiced individually or in concert, has offsetting commercial or performance disadvantages which have precluded significant advances in the development of polish films with improved durability under pedestrian traffic. For example, higher molecular weight vehicles, obtained through modification of the polymerization process or inclusion of specialty polyfunctional monomers or covalent crosslinking agents, are costly to prepare and formulate, and result in polishes with reduced gloss and reduced removability properties. Similarly, high glass transition copolymers obtained through the incorporation of increased levels of the lower alkyl acrylate or methacrylate esters, result in polish vehicles which are expensive to prepare, which require higher levels of expensive plasticizers to obtain low temperature film formation, and which are of reduced gloss. Copolymerizing high levels of styrene monomer with the conventional acrylates used in floor polish vehicles is well recognized to afford high gloss polish vehicles which are typified by poor black heel mark resistance. Reduction of the styrene in these modified-acrylate copolymers will improve the general wear resistance of these polishes, but the improvement occurs at the expense of reduced gloss and poor water resistance and alkaline detergent resistance. Because copolymeric acid functional monomers contribute toward high glass transition temperature, these may be considered a special case of using a harder polymer. The inclusion of increased levels of acid functional, or other polar or polarizable functional monomers, in the copolymer backbone, is practical as a route to improved polish durability. This practice, however, also results in poor performance in terms of storage stability, water resistance, alkaline detergent resistance, compatibility with standard polish formulating ingredients, and recoatability. To some extent these adverse effects of highly functionalized copolymers can be offset by concurrently increasing the level of polyvalent metal crosslinking agent. However, this measure increases cost, reduces gloss, increases plasticizer demand, and has little effect on the stability and compatibility problems. Increasing the level of polyvalent metal crosslinker without concurrently increasing the copolymeric acid content results in increased costs, polymer sedimentation instability, lower polish gloss and leveling performance, and increased plasticizer demand. It is apparent that the practice of the art of floor polish polymer design is a broad compromise between polish durability and a host of other properties desirable in a floor polish film.